November 2, 2023 Outlook: Invest 97L running out of time and a site update!

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One-sentence summary

Invest 97L now seems unlikely to develop, but it will bring a healthy amount of rain and flooding risk to Central America in the coming days.

Invest 97L: Probably out of time to develop, but will still bring big rains to Central America

In the words of the legendary Hall & Oates, “I’m out of time.” Or at least that’s what Invest 97L is saying at this point.

Invest 97L is struggling mightily this afternoon. Development chances have dropped to a paltry 20 percent with this system as it approaches Central America.

There is an invest somewhere in here, but it seems highly unlikely to organize. (Tropical Tidbits)

And judging by the satellite picture I pinned above, even 20 percent might be generous. Whatever the case, an area of disorganized showers and thunderstorms will approach Central America over the next few days. Two things: First, credit to the European model for being very lukewarm on organization with this, whereas the GFS was quite bullish on intensity. Second, this remains a heavy rain and flooding threat for Central America and places ringing the Gulf of Honduras. Rain totals as forecast by various models continue to show anywhere from 5 to 15 inches or even more in spots. I am most concerned about the coast of Honduras, Guatemala, and Belize, as well as far northern Nicaragua.

Rain totals will be significant in Central America, even if 97L never organizes. Flash flooding, mudslides, and problems are likely in this region. (Weathernerds.org)

Rain of this magnitude will likely lead to flash flooding, as well as the potential for mudslides in these areas. And this assumes little to no organization of 97L, so as we have been highlighting, we can view this as a big time rainmaker.

Elsewhere, both the Atlantic and Pacific look quiet over the next week, with no real land issues expected.

The rest of the U.S. looks pretty quiet with no significant extremes in temperature expected over the next 5 days or so. Rain will continue but should be manageable in the Northwest. Mountain snow, not atypical for November will continue in the interior West at times.

November 1, 2023 Outlook: Tropical rains head for Central America while atmospheric river rains head for the Northwest

One-sentence summary

We continue to watch the rain potential from Invest 97L as it tracks toward Central America, while in the U.S., an atmospheric river event will bring locally heavy rain to the Northwest.

Invest 97L: Still watching development chances, but focused more on rainfall

I think we’ve got a bit of a good news/bad news update this morning. The good news is that Invest 97L looks as if it will not be following earlier GFS operational runs, which had this exploding in the southwest Caribbean. Rather, it will be sort of slow getting its act together. The hope is that this will lower the ceiling on 97L’s potential intensity.

Invest 97L on satellite this morning remains very disorganized and void of a lot of thunderstorms near its center. (Weathernerds.org)

In fact, odds of development from the National Hurricane Center have dropped to 50 percent today.

The bad news is that we are still looking at a pretty substantial rain event for portions of Central America, particularly along the coast along the Gulf of Honduras. How much rain? Well, if you believe most model guidance, it should be double digit totals spread out over a few days.

Forecast rain totals through Sunday from the European model suggest 10 inches or more of rain ranging from the extreme southern Yucatan into Belize & Guatemala and along the coast of Honduras. (Weathernerds.org)

This will be capable of causing flooding, mudslides, and general problems. So regardless of what Invest 97L does, at the very least, it should be a significant rainstorm for portions of coastal Honduras, Guatemala, and Belize, as well as perhaps the southern coastal Yucatan and portions of Nicaragua.

In general, 97L will track west or west-southwest over the next few days on a beeline toward Honduras or Nicaragua. We’ll keep tabs on this over the coming days just in case anything changes and obviously to monitor the flooding risks in Central America.

Elsewhere: Moderate to strong atmospheric river event for the Pac Northwest

Pilar is now on its way out to sea in the Pacific and should no longer be an issue for land.

Tropical Storm Pilar is now on its way out to sea. (Tomer Burg)

Some residual rain or localized flooding is possible on the Pacific side of Central America between El Salvador and Costa Rica before things clear out. At this point, impacts from 97L should stay on the Caribbean side of the coast.

Atmospheric river for the Northwest

An atmospheric river (AR) that looks like it should reach level 3 out of 5 on the AR scale will come ashore in Washington or Oregon later this week. ARs of that magnitude are considered strong but offer a general balance of positive and hazardous impacts. Not quite Goldilocks.

The maximum intensity of this atmospheric river based on research is about a level 3 of 5 into Oregon, making it a “strong” AR. (UCSD Center for Western Weather & Water Extremes)

Widespread flooding is not expected, but some localized urban or small stream flooding is possible. The NWS in Seattle has identified the Skokomish River near Potlatch as a possible flooding candidate as well. Rainfall totals are expected to be on the order of 2 to 5 inches with round one that comes ashore tonight into tomorrow.

Snow levels will be high with this event, so you will be mainly talking rain below 8,000 to 10,000 feet. A second atmospheric river (a weaker one) will arrive Saturday and perhaps a third round follows Monday. But the more potent one will be tonight into tomorrow. When all is said and done next week, look for about 2 to 5 inches of rain in the Seattle and Vancouver, BC areas, 3 to 5 inches in the Portland area, and higher amounts at the coast and in the Cascades.

Significant rain will fall from extreme northern California into British Columbia from this atmospheric river event tonight and subsequent weaker ones this weekend. (Pivotal Weather)

Early season chill

Elsewhere, record cold continues in parts of the Appalachians and Deep South tomorrow morning before things begin settling. One impressive record of note may occur in Caribou, Maine which is forecast to hit 12 degrees tonight and Thursday morning. This would be the second earliest date they’ve been this cold. The only time better was when they hit 12 degrees back on November 1, 1972.

A map of Thursday morning’s forecast lows that are near records. The most impressive would probably be in Caribou, ME which may record their second earliest coldest temperature since 1939. (NOAA WPC)

Brrr! More tomorrow.

October 31, 2023 Outlook: Caribbean’s Invest 97L is likely to bring some sort of impacts to portions of Central America

One-sentence summary

Invest 97L in the Caribbean is likely to deliver impacts to portions of Central America in several days, but the exact issues beyond heavy rain and flooding potential remain unclear at this time.

Invest 97L: A troublemaker for the southwest Caribbean

We finally got the Caribbean disturbance a classification yesterday. It is Invest 97L. As we noted yesterday, this one will bear close watching for folks in Central America in particular.

Invest 97L saw a big flare up in storms overnight that is already weakening. (Weathernerds.org)

Thunderstorms really popped with 97L overnight, but in the last few hours those storms have begun to steadily weaken. In order for 97L to develop, it will need to be able to sustain thunderstorm activity.

In general, 97L is going to be steered west or just south of west around the periphery of high pressure over the open Atlantic. This will take it on a beeline toward Central America. Unfortunately once it gets there, it looks like it may slow down. This could lead to a considerable rainfall event for portions of the region. In fact both the GFS and European operational models, despite vastly different intensity outcomes each produce nearly double digit rainfall totals through early next week in portions of Central America, particularly near the coasts of Honduras, Guatemala, and Belize.

Rain totals of at least 5 to 10 inches seem like a good bet somewhere near the coasts of Honduras, Guatemala, or Belize as 97L (or whatever it is then) approaches. (Weathernerds.org)

So we have two aspects of this system that will give us heartburn in the coming days. The rainfall is one, but the intensity of the storm is another. As I noted above, the GFS and European models have been on different planets in terms of what they do with 97L. The GFS continues to be very aggressive, while the European model is far slower to develop the system.

We often get asked “Well, which one do you believe?” The answer is not so simple. The GFS suite tends to develop more persistent thunderstorm activity with 97L, giving it more time to feed on the extremely warm Caribbean waters. The Euro is less excited about persistent thunderstorms at the core, so it remains a rainmaker but not so much a wind-maker. We’ll get a better sense in the next day or so based on the actual speed in organization of the system.

Again, however, the rainfall forecast is already somewhat concerning, so whether or not this becomes a stronger storm will probably not exempt portions of Central America from some noteworthy impacts. We’ll have more on this tomorrow.

Other news: Pilar, record cold, and a wet Northwest

Tropical Storm Pilar will make its 180 degree turn today on approach to El Salvador, shifting back west out into the open Pacific. Conditions should improve in that portion of Central America.

Pilar will be making a J-turn over the next 24 to 36 hours heading back out into the open Pacific. (Tomer Burg)

Meanwhile, early season cold continues across much of the country. Quite a few spots will threaten record lows tomorrow morning, ranging from the Ohio Valley into Texas. Places like Oklahoma City and St. Louis are forecast to just eke out new records, while about 35 other locations are within a degree or two of records. Temperatures should moderate for the end of the week.

A map of Wednesday morning’s forecast low temperatures that will be near records, featuring just over 35 locations that will be close. (NOAA WPC)

Otherwise, the only real U.S. weather of note for the rest of the week will be a series of storms into the Pacific Northwest that we discussed a bit yesterday.

October 30, 2023 Outlook: Hurricane season won’t exactly go away quietly

One-sentence summary

The tropics refuse to go away quietly, with Pilar in the Pacific and a potential Caribbean system later this week that bears watching in Central America.

Atlantic update: Invest 96L unlikely to do much, but the Caribbean bears watching later this week

We are watching two areas in the Atlantic at the moment: Invest 96L near the Bahamas and a yet-to-develop system in the Caribbean. Let’s run through them.

Invest 96L

Though this is the most immediate item on the menu, it’s not the most notable. 96L was found with gusty winds but no real circulation to hone in on yesterday, so it remains just a disturbance. But it’s about to get smacked in the face by dry air and wind shear, as the much discussed significant U.S. cold front comes sweeping offshore tomorrow.

Invest 96L will soon run out of time to develop east of the Bahamas, as a cold front will sweep it away. (Weathernerds.org)

This should knock 96L out to sea and probably prevent any real development at all.

Caribbean

Despite their noisy operational guidance shows, both the GFS and European models are in decent agreement right now that a surface low pressure system is going to form in the Caribbean around midweek. It will drift west in the coming days toward Central America. Both sets of ensembles (which run the models 30 to 50 different times) show a favorable setup for development, but the GFS is tending to run “hot” right now, developing it slowly but intensely as it comes west. The Euro? Not so much. But this has been an issue throughout hurricane season. The GFS does tend to overcook Caribbean systems this time of year, and the Euro has tended to have an underforecast bias when it comes to intensity. To me, that argues for some type of developing tropical system in the western Caribbean by the weekend.

The average of all the GFS ensemble members for Wednesday evening shows a developing system south of Hispaniola in the Caribbean, likely to track due west or even west-southwest. While the GFS operational may be too aggressive at this point, this system will bear close watching in Central America. (Tropical Tidbits)

In general, I would expect this system to be steered generally west, if not even a little south of west around the periphery of sprawling high pressure that will extend from south of Bermuda across the Bahamas toward Cuba and the Yucatan this weekend. Exactly how far west this gets, how strong it gets, and where (if) it makes landfall is to be determined, but interests from the Yucatan and Belize south into Honduras and Nicaragua should probably be watching this rather closely in the meantime. We’ll update with the latest tomorrow.

Pacific Update: Pilar will likely bring heavy rain to El Salvador

Tropical Storm Pilar formed last night in the eastern Pacific. Over the next couple days it will drift toward El Salvador and Honduras. Tropical Storm Watches are posted there and Nicaragua. Pilar is not currently expected to become a hurricane, and it will primarily bring tropical storm conditions and heavy rain to the Pacific coastal communities between Guatemala and Nicaragua. Heavy rain could cause flooding and mudslides in some of these areas.

Pilar will take a funky track toward El Savador and Honduras over the next 36-48 hours before pulling a 180 and heading out to sea. (Tomer Burg)

Elsewhere in the East Pac, we don’t expect any significant development through the week.

U.S. Weather: Frost & freeze & Santa Ana winds in California

If you look at a National Weather Service hazards map of the U.S. right now, one thing sure stands out: Frost and freeze alerts all over the place. Freeze warnings extend from the Mexico/New Mexico border up into Ohio and Pennsylvania.

Freeze warnings extend from Arizona and the New Mexico border with Mexico up into Pennsylvania this morning. (Pivotal Weather)

Some cold nights are ahead this week with the first true wintry-type air mass of the season across the Lower 48.

And as is often the case, when cold air dumps into the Rockies and points east, Santa Ana winds are kicking up in California, leading to warm weather and critical fire danger today, particularly in the higher terrain around Los Angeles and into Ventura County.

A fairly classic Santa Ana wind pattern across metro SoCal today. The strongest winds and highest fire danger today will be in the mountains around LA, as well as in Ventura County. (Pivotal Weather)

We’ll hope for nothing serious in that part of the country. Winds should settle down on Tuesday.

Otherwise, it looks like a relatively quiet week nationally. A storm will enter the Pacific Northwest around Thursday, bringing heavy rain and mountain snow. Snow levels will be relatively high with these storms. That may be followed by a second or third system this weekend.

Mostly welcome precipitation over the next week will be fairly considerable from northern California into the Northwest, though snow levels will be a bit high. (Pivotal Weather)

We’ll keep tabs on all that as well.